clara con limon / cerveza con limon

need a recipe:

so far i've seen:
1/2 pilsner 1/2 fanta lemon (which i can't find)
1/2 pilsner 1/2 san pellegrino limonata (which doesn't taste quite right)
3/4 estrella beer and 1/4 schwepps limon

before i go blow more money on beer, does anyone have better sources of a great tasting clara con limon? (yes, i've googled, yes, i've used babelfish to yield poorly translated Spanish web pages, etc.)